objectModel - The Map with object of the
calling environment which can be used
to select values this controller may need
(ie Request, Response).

source - A source String to the Action

param - The Parameters for this invocation

Returns:

Map The returned Map object with
sitemap substitution values which can be used
in subsequent elements attributes like src=
using a xpath like expression: src="mydir/{myval}/foo"
If the return value is null the processing inside
the element of the sitemap will
be skipped.